1. Technical Field
The invention relates to a projection zoom lens device having a five-group configuration and being mounted on a projection-type display apparatus and to a projection-type display apparatus having the projection zoom lens device, and particularly, to a projection zoom lens device configured so that a light flux containing image information, which is generated from a light valve such as a liquid crystal display device or a DMD (Digital Micromirror Device) display device, is magnified and projected onto a screen, and a projection-type display apparatus.
2. Description of Related Art
Recently, a projection-type display apparatus using a light valve such as a liquid crystal display device or a DMD display device has come into widespread use. In particular, the most widely used is a projection-type display apparatus having the configuration that respective illumination light are modulated by using three light valves so that these light valves correspond to the illumination light of ROB three primary colors, the light modulated by the respective light valves are synthesized by a prism or the like, and an image is displayed onto a screen through a projection lens device.
A decrease in size and an increase in accuracy are rapidly progressing in the light valve. Besides, with an increase in spread of PCs, the demands of performing presentation using such a projection-type display apparatus increases. Hence, a demand for a more high-performance and more small-sized lightweight projection-type display apparatus arises.
Specifically, in a projection-type display apparatus that synthesizes and projects the modulated light from the three light valves by using the color synthesizing optical system, there is required a long back focal length in order to arranging a prism and the like which synthesize colors, because of a characteristic of a projection lens. In addition, in a color synthesizing optical system, spectrum characteristic thereof is changed depending on an angle of incident light. Thus, the projection lens is required to have telecentricity, which is defined as a characteristic of a telemetric system in which an entrance pupil is at infinity when viewed from a reduction side. Also, there is required aberration correction appropriate to resolution of the device, and there is also required a zoom function in view of installation convenience.
JP 2000-137165 A and JP 2001-91829 A disclose projection lens devices satisfying the conditions mentioned above. The lens devices have a five-group configuration of negative, positive, positive, positive (or negative) and positive refractive power in order from a magnification side. In the lens devices, during zooming, the second lens group, the third lens group, and the fourth lens group are moved in an optical axis direction while the first lens group and the fifth lens group are fixed.
However, with regard to the projection zoom lens device described in JP 2000-137165 A and JP 2001-91829 A, further improvement in longitudinal chromatic aberration is demanded.
In particular, when the projection zoom lens device is used in a projection-type display apparatus in which the entire projection zoom lens device is replaceable, even in terms of longitudinal chromatic aberration, it is required to sufficiently correct aberrations solely by the projection zoom lens device. Therefore, in this point of view, the projection zoom lens devices described in JP 2000-137165 A and JP 2001-91829 A have room for improvement.